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/sci/ - Science & Math

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7441155 No.7441155 [Reply] [Original]

Electrons - they orbit the nucleus in elliptical/circular paths. A change in direction requires force. I assume this force comes from the electromagnetic force between the protons and electrons. However, to change an electrons direction requires the expenditure of energy. Where does this energy come from? Is the nucleus losing energy during this process? If so, that should be measurable. Has it been? If it hasn't, my next question is what is "recharging" the atom so we don't observe lost energy?

Pic not really related

>> No.7441161

>>7441155
thats not how it works

>> No.7441168

nuclear orbits are regions of equal energetic potential

it takes no energy at all to stay in one orbit

>> No.7441169

>>7441155
>Electrons - they orbit the nucleus in elliptical/circular paths

Actually, they don't. This has been known ever since quantum theory took over in the twenties. At atomic scales, electrons behave as waves - around an atom, electrons exist as bound standing waves.

>> No.7441184

>>7441168
If it doesn't take energy, then how can the path curve?

>> No.7441191

>2015
>replying to b8 threads

>> No.7441193

>>7441191
I don't think it's bait, I think it is just a highschooler who wants some clarification on intro chem.

>> No.7441204

>>7441184
It doesn't. The electrons don't "orbit" at all; this is a simplified picture that has not been part of scientific theory since the 20s, because it has major problems and didn't fit the facts.

It is occasionally brought up as a simplified, "lies to children" way of explaining electron behavior, but it is completely wrong.

>> No.7441220

>>7441204
I've studied electron clouds/orbitals. I always thought that just represents a probability of where the electronic might be found at any time. What is the alternative explanation? That electrons become delocalized clouds until a measurement is made which collapses the wave function?

>> No.7441242

>>7441204
Fuck this bullshit.

Why the fuck did I spend so long in highschool chem learning shit like this and VSEPR when it's all goddamn bullshit and lies.

why can't we just teach kids the truth?

Seriously, the last three years of undergrad chem have just been slowly unlearning all the bullshit they shoved me in highschool. Why is this allowed?

>> No.7441271

>>7441242
congratulations, that's every level of chemistry education up to and including graduate school

>> No.7441278

>>7441220
>I've studied electron clouds/orbitals. I always thought that just represents a probability of where the electronic might be found at any time.

Specifically, they represent the *amplitude* of the electron wave. The probability of finding the electron when the cloud is interacted with is the square of the amplitude.

>> No.7441279

>>7441242

You never should have been taught that electrons are little balls that go in circles around the nucleus. I wasn't. Maybe you just misundersrood at the time?

>> No.7441291

>>7441242
Because real chemistry is too complicated, and things like VSEPR are good approximations that give students a decent understanding of what kinds of things chemistry can do.

Same reason physics starts with Newton before bringing in Einstein.

>> No.7441314

>>7441220
It is delocalized. That's the whole point. An accelerated, charged particle radiates and thus loses energy.
Electrons however don't - quantum mechanics is born.

>> No.7441733

Okay, how about this then:

What source of energy curves the orbits of the planets around the sun? Where is energy being consumed so that the planets can have their directions changed?

>> No.7441744

>>7441733
Energy doesn't depend on direction. Kinetic energy depends only on speed and mass. So a planet traveling in one direction has the same energy no matter how that direction changes.

Therefore, it takes no energy to infinitesimally change the direction of a planet's motion, and thus no energy to keep an orbiting body in orbit.

>> No.7441758

>>7441733
Nowhere. Unlike momentum, kinetic energy just depends on *speed*, not direction; only speeding up and slowing down a moving body involve changes in kinetic energy.

And gravitational potential energy depends only on mass and distance from other masses.

So if speed, mass, and distance from other masses aren't changed, then there's no change in energy.

Imagine a dumbbell, spinning in the frictionless vacuum of space around its center of mass. Surely, this takes no energy to continue spinning? What if we replaced the center bar with a string? A spring?

>> No.7443139

>>7441155
implying the bohr model is still in use.

>> No.7443584

>>7441744
>>7441758

I thought kinetic energy includes mass and velocity. Velocity is not speed, it has a direction because it is a vector.

If I'm driving my car and I change direction, surely energy was transferred. The frame of my car heats up by flexing during the turn. The road heats up by serving as the other side of the energy equation, absorbing force and converting it into heat at the molecular scale.

>> No.7443640

>>7443584
>I thought kinetic energy includes mass and velocity. Velocity is not speed, it has a direction because it is a vector.

It does include velocity - velocity *squared.* What that actually means is that you take the dot product of the velocity vector with itself ... which is a regular scalar, equal to the magnitude squared. In other words, all that matters is the speed, not the direction, because any direction gives the same squared magnitude and thus the same energy.

>If I'm driving my car and I change direction, surely energy was transferred. The frame of my car heats up by flexing during the turn. The road heats up by serving as the other side of the energy equation, absorbing force and converting it into heat at the molecular scale.

Yeah, but that's one of those second-order effects like drag and friction; it only exists because your car has thickness and volume. We're pretending planets are point masses, like Newton did.

This flexing *does* occur, and does take energy - the effect is known as "tides." But for point masses, where there's no gravity gradient, it is ignored like other complicating effects in Physics Class Land.

If your car was a rigid body or a point mass, it likewise wouldn't flex and so no energy exchange would be involved - only exchange of momentum. It could be placed on a frictionless track and keep going around and around forever with no energy input.

>> No.7443748

>>7443640

Thank you for the informative answer. Using your car and frictionless track example, the car can go in a circle forever with no energy input because the frictionless track is there to turn the car. Is there an equivalent of the track for a planet orbiting a star? Is that gravity? Am I basically asking "What is gravity?"

>> No.7443752

>>7441155
>Electrons - they orbit the nucleus in elliptical/circular paths.
Stopped reading right there.

>> No.7443769

>>7443139
Back in its day, the Bohr atom was right, and science was proud.

A generation later, the Bohr atom was laughably wrong, and science was proud of finding out it had been wrong all along.

Nothing changes. Science is always wrong.

>> No.7443827

>>7443748
>Is there an equivalent of the track for a planet orbiting a star? Is that gravity? Am I basically asking "What is gravity?"

Yep, that's gravity. In the same way as the curving track provides a constant centripetal push, gravity provides a constant centripetal pull.

Gravity is a field, like the electrical and magnetic field, emanating from all objects with mass. Indeed, we could call mass "gravitational charge." Like a stretched spring, all objects with mass attract each other, with attraction depending on distance. (Unlike a stretched spring, gravity gets weaker with distance, following an inverse-square law; twice as far is four times as weak, thrice as far is nine times as weak). Also like a stretched spring - and like other fields, such as electrical and magnetic fields - energy can exist in the gravitational field itself - we call this "gravitational potential energy." As an object falls, the spring relaxes, and that potential is converted to kinetic energy.

(The preceding explanation was importantly wrong, because it ignores relativity, but it'll do well enough)

>>7443769
>Nothing changes.
>Science is always wrong.

Once, people said the Earth was flat, and they were wrong.

Once, people said the Earth was a sphere, and they were wrong.

Once, people said the Earth was an oblate spheroid with such-and-such parameters, and they were wrong.

But if you think that all these people were equally wrong, you are wronger than all of them put together.

>> No.7443872

>>7443748
>Is there an equivalent of the track for a planet orbiting a star? Is that gravity? Am I basically asking "What is gravity?"

This is a very handwavy explanation based on my vague understanding of relativity, but I'll give it a shot.

You know how people keep talking about gravity "curving spacetime"? Now you know what they mean.

On its own, a particle with mass will move in a straight line, not slowing or speeding up or changing direction. (As would your car, if there were no curved track.)

However, gravity causes space-time to curve. This changes the coordinate system - such that a "straight line" is no longer straight. Particles travel along geodesics, the shortest paths between two points. In flat uncurved space, these geodesics are what we'd call straight lines; in curved space, these geodesics appear to be curves. (For instance, on a sphere like Earth, the shortest surface path between the North and South poles is very obviously curved. On our curving track, if we want to go between two points on the track without leaving the track, we must follow its curve.)

Gravitational force, in this view, is a "fictitious force" much like the centrifugal force on our curving track, caused by the particle moving along curved spacetime.

https://en.wikipedia.org/wiki/Introduction_to_general_relativity

>> No.7443893

>>7443827
I'm genuinely curious, why isn't the Earth an oblate spheroid? I thought it was. Are you referring to the fact that it has mountains and so, and it can't be called an spheroid because of that?

>> No.7443903

>>7443748
>Is there an equivalent of the track for a planet orbiting a star?

Yep. Every particle in the universe can be thought of as following its own "track" (world-line) through space and time. Where these tracks curve, we say that space-time is curved. And as the particle travels along a curved track, it feels a force, just like you feel a force when going along turns in your car - gravitational force.

Space-time tells matter how to move; matter tells space-time how to curve.

>> No.7443905

>>7441155
> they orbit the nucleus in elliptical/circular paths
they dont

>> No.7443908

>>7443872
>Gravity is fictitious.

Stay wrong /sci/.

>> No.7443911

>>7443893
>I'm genuinely curious, why isn't the Earth an oblate spheroid? I thought it was. Are you referring to the fact that it has mountains and so, and it can't be called an spheroid because of that?

The South hemisphere bulges very slightly compared to the North hemisphere, making Earth very very very slightly pear-shaped.

(The effect is slight enough that earth measurements generally just ignore it completely, keep considering the Earth as an oblate spheroid, and account for it in the "geoid" - the corrections for how Earth's gravity slightly deviates from what you'd expect of a perfect, constant-density oblate spheroid)

>> No.7443913

>>7443827
>But if you think that all these people were equally wrong, you are wronger than all of them put together.

I'm glad you agree with me that science is always wrong.

When the goal is to be right, being wrong in any measure is total and absolute failure.

The myth that science is closing in on the truth is also a lie. Despite your perceptual hallucinations regarding the "evolving" shape of the earth.

>> No.7443921

>>7443908
"Fictitious force" just means it can be eliminated by the correct choice of coordinate system and reference frame. (For instance, centrifugal force is "ficticious" because it disappears if you choose a reference frame in which you are rotating around a point.)

For point test particles, gravity also disappears in the right reference frame - the big insight of general relativity is that gravity is locally indistinguishable from acceleration.

(Of course, if you look at more than one point at once, you can determine if it's real gravity or not - only real gravity has tidal effects, where two relatively stationary points at different locations feel different forces.)

>> No.7444520
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7444520

>>7443913
>implying "wrong" is absolute
absolutist GTFO